Car Alarm

[david61]

My car alarm seems to go off for no reason whatsoever. No one tampering with it or sitting inside when doors locked

[Fitter]

My car alarm seems to go off for no reason whatsoever. No one tampering with it or sitting inside when doors locked

Car alarm has ultrasonic sensors. Have you anything in the car that can move. eg seat belts not stored properly, dangling ornaments, loose wires or leaving a window partially open. Any electrical equipment causing a voltage drop. Fitter

[Pat2u]

As already mentioned by fitter, the alarm works on a voltage drop several other causes could be a cell down in the Battery or a bad earth causing a voltage leak, i think i would start by having the Battery checked and a good garage could also diagnose a possible bad earth.

[Jamesbelfast]

One of the most common faults on any alarm system is due faulty bonnet switches.

Check it out first - if necessary tape in down as a test.

Next if there any interior sensors also tape over them.

If neither pf these help then the problem lies elsewhere.

Also check the Battery conections are clean and sound.

Are any additional electrics or electronics fitted (phone connections, etc.) - if so temporary disconnect them.

All these checks can be done easily and cheaply and although may not dure the problem it will help narrow the search.

[Luthier]

Even something as simple as a lone fly in the car can set it off. I know as I had that problem for several days until I spotted it. A bit annoying but relieved it didn't cost me anything!

[Darius28]

My alarm used to go off randomly. Went to check the Battery life, it was very low, so after changing to the new one everything is fine.

[TonyV5]

Will a fast temperature rise or heat eddy currents trigger the ultrasonic sensor?

[Pat2u]

Will a fast temperature rise or heat eddy currents trigger the ultrasonic sensor?

No its a voltage drop or vibration that triggers the alarm.

[TonyV5]

Is the vibration sensor adjustable? it was a bit windy one day it when off.

[Pat2u]

A car going by at speed can trigger the alarm, but i would think if its going off regular i would be looking for a voltage drop.

[bestseany]

You can temporarily disable the interior sensors to eliminate them. There should be a button near the front interior light to disable them.

[gargol]

Hi

Wwhen I had a 2009 Avensis I had a problem when it rained heavily, not water getting in , but dealer knew of a problem with the new model and fitted insulation to the alarm module thta cured it.

Only ever went off when it rained hard, info was passed via the dealer network, not by Toyota.